There are two basic types of self-steering devices which are presently employed to control course automatically on sailing vessels. The first of these are electronic self steerers which are designed and constructed to follow a compass course regardless of the direction or velocity of the wind. This is accomplished by providing a small electric motor which is activated each time the vessel turns away from the desired compass course. The motor turns the rudder until the boat is once more headed in the desired direction.
While electric self steerers do achieve the desired goal of automatic course control, they do suffer from deficiencies as well. For example, electric self steerers obviously require a continuous and sufficient source of current which is not always readily available on a sailing vessel. Moreover, in the event that the wind veers to a point directly ahead of the vessel, the vessel will stop as it cannot sail any closer than a 35 degree angle to the source of the wind. If the vessel's sails are trimmed for sailing close to the wind (beating) and the wind veers so that its source is broadside to the boat, the vessel will be overtrimmed and in strong winds serious damage may result.
Another type of self-steerer known in the art employs "wind vanes" which are set to keep vessels on the same angle to the wind. The wind vane device is mounted on the stern of the vessels and is either linked to the tiller or it may have its own steering oar. In operation, the vessel is set on course and the leading edge of the wind vane is faced directly into the wind. If the vessel wanders the side of the wind vane is presented to the wind. The wind turns the vane, which then turns the tiller and rudder or its own steering oar, until the boat returns to its desired course. Problems which are associated with the use of wind vanes can be summarized as follows. Wind vanes are subjected to tremendous stress and thus require very heavy mountings on the stern of the vessel. The mounts tend to be unsightly and cumbersome. The vanes have to be large and strong enough to stand up to heavy winds. In strong winds the strain on these devices is tremendous. Steering oars frequently break and the control linkage is subjected to prolonged chafing thus producing a tendency to fail. Yet conversely the vanes have to be large and light enough to respond to light winds so they can still develop enough force to overcome the friction and inertia in the system.